1. Technical Field
The present invention relates to an amorphous calcium phosphate catalyst for use in production of 1,3-butadiene and methyl ethyl ketone from 2,3-butanediol, and a method of preparing the same. More particularly, the present invention relates to an amorphous calcium phosphate catalyst containing phosphoric acid and calcium, a preparation method thereof and a method of producing 1,3-butadiene and methyl ethyl ketone from 2,3-butanediol using the amorphous calcium phosphate catalyst.
2. Description of the Related Art
1,3-butadiene is widely utilized as a synthetic rubber material for use in car tires. When it is polymerized with styrene and acrylonitrile, synthetic rubber products such as ABS, NBR and SBR are obtained.
1,3-butadiene is prepared as a byproduct in the course of steam cracking crude oil to obtain ethylene and olefin. It may be prepared via oxidative dehydrogenation of n-butane or butene. In the United States and the Former Soviet Union in the past, an alcohol produced from grain was dehydrogenated and simultaneously condensed in the presence of a metal oxide catalyst, and thus converted into 1,3-butadiene.
In particular, preparation of 1,3-butadiene was under active study by IG Farben in Germany during World War II. The process of producing 1,3-butadiene devised by IG Farben includes converting coal-derived acetylene into acetaldehyde or acetol to prepare 1,3-butanediol that is then reacted in the presence of an acid or base catalyst to thus be converted into 1,3-butadiene.
U.S. Pat. No. 1,984,055 discloses conversion of 1,3-butanediol into 1,3-butadiene using a catalyst comprising sodium hydrogen phosphate, calcium-ammonium phosphate and sodium n-butylamine phosphate. These catalysts are reported to show 1,3-butadiene selectivity of at least 85% and superior durability.
Also, in U.S. Pat. No. 2,386,324, attempts have been made to convert a 1,3-butanediol aqueous solution into 1,3-butadiene using a diammonium phosphate catalyst, leading to a yield of 50% based on evaluation results over 56 days.
Meanwhile, methyl ethyl ketone (MEK) is produced via dehydrogenation from 2-butanol using a catalyst such as Cu or Zn, and may be obtained via a liquid oxidation reaction of a carbon compound resulting from a Fischer-Tropsch process or a heavy naphtha process.
Recently, techniques for converting 2,3-butanediol produced via fermentation into 1,3-butadiene are known, in addition to intermediate products obtained from petrochemical processes. International Publication No. WO 2009151342 discloses production of 2,3-butanediol from syngas via microorganism fermentation, and the produced 2,3-butanediol may be converted into 1,3-butadiene and methyl ethyl ketone using a catalyst.
Korean Patent Application Publication No. 10-2012-0099818 discloses the use of a cesium oxide-silica catalyst so that a sum of 1,3-butadiene and methyl ethyl ketone selectivity is 95% in the temperature range of 400˜500° C.
Meanwhile, Korean Patent No. 1287167 discloses preparation of calcium phosphate catalysts having hydroxyapatite (HAP) and calcium pyrophosphate structures and combinations thereof. These catalysts are calcium phosphate compounds represented by Ca5(PO4)3OH and Ca2(P2O7) with specific crystalline structures. When such catalysts are thermally treated at 300˜700° C. and applied at a temperature of 380° C. and a pressure of 2 atm, 1,3-butadiene is produced in an amount of 25.2% under the condition that a maximum amount of methyl ethyl ketone is 64.5%. Furthermore, when 1,3-butadiene is produced in a maximum amount of 37.4%, methyl ethyl ketone is obtained in a maximum amount of 50.4%.
Korean Patent No. 1298672 discloses addition of alumina to hydroxyapatite to increase 1,3-butadiene selectivity, and thus the 1,3-butadiene selectivity is reported to be 61% based on the reaction results at 360° C. In these patents, the calcium phosphate catalyst has a hydroxyapatite structure or a calcium pyrophosphate structure.
A calcium phosphate catalyst is known to be formed in various phases, depending on the kind of precursor used for catalyst preparation, pH upon catalyst synthesis and control thereof, and the ratio of Ca to P therein.
Calcium phosphate phases are mentioned by Acta Biomaterialia 6 (2010) 4457. Calcium phosphates may include, depending on the ratio of Ca to P therein, monocalcium phosphate (Ca(H2PO4)2, Ca/P=0.5), dicalcium phosphate (CaHPO4, Ca/P=1.0), tricalcium phosphate (Ca3(PO4)2, Ca/P=1.50), octacalcium phosphate (Ca8(HPO4)2(PO4)4, Ca/P=1.33), hydroxyapatite (Ca5(PO4)3(OH), Ca/P=1.67), and amorphous calcium phosphate (CaxHy(PO4)z.nH2O n=3˜4.5, 15˜20% H2O). Furthermore, mutual phase transformation is known to occur during thermal treatment after preparation of the catalyst.